Cisco Adaptive Security Appliance Remote Code Execution and Denial of Service Vulnerability

Summary

• Update from February 5, 2018: After further investigation, Cisco has identified additional attack vectors and features that are affected by this vulnerability. In addition, it was also found that the original fix was incomplete so new fixed code versions are now available. Please see the Fixed Software section for more information.
  
  

  ---

  
  A vulnerability in the XML parser of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause a reload of the affected system or to remotely execute code. It was also possible that the ASA could stop processing incoming Virtual Private Network (VPN) authentication requests due to a low memory condition.
  
  The vulnerability is due to an issue with allocating and freeing memory when processing a malicious XML payload. An attacker could exploit this vulnerability by sending a crafted XML packet to a vulnerable interface on an affected system. An exploit could allow the attacker to execute arbitrary code and obtain full control of the system, cause a reload of the affected device or stop processing of incoming VPN authentication requests.
  
  To be vulnerable the ASA must have Secure Socket Layer (SSL) services or IKEv2 Remote Access VPN services enabled on an interface. The risk of the vulnerability being exploited also depends on the accessibility of the interface to the attacker. For a comprehensive list of vulnerable ASA features please refer to the table in the Vulnerable Products section.
  
  Cisco has released software updates that address this vulnerability. There are no workarounds that address all the features that are affected by this vulnerability.
  
  This advisory is available at the following link:
  https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180129-asa1

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASA Software that is running on the following Cisco products:
  

  • 3000 Series Industrial Security Appliance (ISA)
  • ASA 5500 Series Adaptive Security Appliances
  • ASA 5500-X Series Next-Generation Firewalls
  • ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers
  • ASA 1000V Cloud Firewall
  • Adaptive Security Virtual Appliance (ASAv)
  • Firepower 2100 Series Security Appliance
  • Firepower 4110 Security Appliance
  • Firepower 4120 Security Appliance
  • Firepower 4140 Security Appliance
  • Firepower 4150 Security Appliance
  • Firepower 9300 ASA Security Module
  • Firepower Threat Defense Software (FTD)
  • FTD Virtual (FTDv)

  ASA Software

  In the following table, the left column lists the vulnerable Cisco ASA features. The right column indicates the vulnerable configuration from the CLI command show running-config, if it can be determined.
  
  

  Feature	Vulnerable Configuration
  Adaptive Security Device Manager (ASDM)1	http server enable http
  AnyConnect IKEv2 Remote Access (with client services)	crypto ikev2 enable client-services port webvpn anyconnect enable
  AnyConnect IKEv2 Remote Access (without client services)	crypto ikev2 enable webvpn anyconnect enable
  AnyConnect SSL VPN	webvpn enable
  Cisco Security Manager2	http server enable http
  Clientless SSL VPN	webvpn enable
  Cut-Through Proxy (Not vulnerable unless used in conjunction with other vulnerable features on the same port)	aaa authentication listener port
  Local Certificate Authority (CA)	crypto ca server no shutdown
  Mobile Device Manager (MDM) Proxy3	mdm-proxy enable
  Mobile User Security (MUS)	webvpn mus password mus server enable port mus
  Proxy Bypass	webvpn proxy-bypass
  REST API4	rest-api image disk0:/ rest-api agent
  Security Assertion Markup Language (SAML) Single Sign-On (SSO)5	N/A

  ¹ASDM is vulnerable only from an IP address in the configured http command range.
  ² Cisco Security Manager is vulnerable only from an IP address in the configured http command range.
  ³The MDM Proxy is first supported as of software release 9.3.1.
  ⁴The REST API is first supported as of software release 9.3.2. The REST API is vulnerable only from an IP address in the configured http command range.
  ⁵SAML SSO is first supported as of software release 9.6.
  
  The customer can also use the show asp table socket | include SSL|DTLS command and look for an SSL or a DTLS listen socket on any TCP port. If either socket is present in the output and the ASA device is configured for one or more of the ASA features in the above table, the device is considered vulnerable. The following example shows an ASA device with SSL and DTLS listen sockets:
  

  ciscoasa# show asp table socket | include SSL|DTLS
  SSL       00185038  LISTEN     172.16.0.250:443    0.0.0.0:*
  SSL       00188638  LISTEN     10.0.0.250:443      0.0.0.0:*
  DTLS      0018f7a8  LISTEN     10.0.0.250:443      0.0.0.0:*    

  The customer can also check the show asp table socket stats protocol ssl command to list the underlying SSL system statistics. The SSL statistics indicate the number of each type of message received and is further verification that the ASA device is vulnerable.
  

  ciscoasa# show asp table socket stats protocol ssl
  NP SSL System Stats:
    Handshake Started:          83
    Handshake Complete:         60
    SSL Open:                    7
    SSL Close:                 285
    SSL Server:                 84
    SSL Server Verify:           0
    SSL Client:                  0

  Note: While certain IKEv2 feature sets do not enable the underlying SSL TCP listening socket, they may still be vulnerable. Customers can use the CLI command show running-config crypto ikev2 to check if the configuration command crypto ikev2 enable is present in the configuration.
  

  ciscoasa# show running-config crypto ikev2 | include enable
  crypto ikev2 enable Outside

  If a command like crypto ikev2 enable is present in the running configuration and the command anyconnect enable is part of the global webvpn configuration, the ASA device is also considered vulnerable.
  
  Determining the ASA Running Software Release
  
  To determine whether a vulnerable release of Cisco ASA Software is running on a device, administrators can use the show version command in the CLI. The following example shows the output of the command for a device that is running Cisco ASA Software Release 9.2(1):
  

  ciscoasa# show version | include Version
  Cisco Adaptive Security Appliance Software Version 9.2(1) 
  Device Manager Version 7.4(1)

  Customers who use Cisco Adaptive Security Device Manager (ASDM) to manage devices can locate the software release in the table that appears in the login window or the upper-left corner of the Cisco ASDM window.
  
  FTD Software
  
  This vulnerability applies to all FTD releases before the first fixed software release. The FTD release contains both Firepower and ASA code. Please review the Firepower Threat Defense Devices section in the Cisco Firepower Compatibility Guide for additional information.
  
  In the following table, the left column lists the vulnerable Cisco FTD features. The right column indicates the vulnerable configuration from the CLI command show running-config, if it can be determined.
  
  

  Feature	Vulnerable Configuration
  HTTP Service enabled1	http server enable http
  AnyConnect IKEv2 Remote Access (with client services)2,3	crypto ikev2 enable client-services port webvpn anyconnect enable
  AnyConnect IKEv2 Remote Access (without client services)2,3	crypto ikev2 enable webvpn anyconnect enable
  AnyConnect SSL VPN2,3	webvpn enable

  ¹ The HTTP feature is enabled via Firepower Threat Defense Platform Settings > HTTP on the Firepower Management Console (FMC).
  ² Remote Access VPN features are enabled via Devices > VPN > Remote Access on the FMC or via Device > Remote Access VPN on the Firepower Device Manager (FDM).
  ³ Remote Access VPN features are first supported as of software release 6.2.2.
  
  The customer can also use the show asp table socket | include SSL|DTLS command and look for an SSL or a DTLS listen socket on any TCP port. If either socket is present in the output and the FTD device is configured for one or more of the features listed in the above table, the device is considered vulnerable. The following example shows an FTD device with SSL and DTLS listen sockets:

  firepower# show asp table socket | include SSL|DTLS
  SSL       01ffb648  LISTEN     1.1.1.1:443         0.0.0.0:* 
  DTLS      00009438  LISTEN     1.1.1.1:443         0.0.0.0:*

  The customer can also check the show asp table socket stats protocol ssl command to list the underlying SSL system statistics. The SSL statistics indicate the number of each type of message received and is further verification that the FTD device is vulnerable.
  

  firepower# show asp table socket stats protocol ssl
  NP SSL System Stats:
    Handshake Started:          44
    Handshake Complete:         42
    SSL Open:                    2
    SSL Close:                  77
    SSL Server:                 45
    SSL Server Verify:           0
    SSL Client:                  0

  Note: While certain IKEv2 feature sets do not enable the underlying SSL TCP listening socket, they may still be vulnerable. Customers can use the CLI command show running-config crypto ikev2 to check if the configuration command crypto ikev2 enable is present in the configuration.
  

  firepower# show running-config crypto ikev2 | include enable
  crypto ikev2 enable Outside

  If a command like crypto ikev2 enable is present in the running configuration and the command anyconnect enable is part of the global webvpn configuration, the FTD device is also considered vulnerable.
  
  Determining the Running FTD Software Release
  
  Administrators can use the show version command in the CLI to determine the FTD release. In this example, the device is running software release 6.2.2:
  

  > show version
  ---------------------[ ftd ]---------------------
  Model : Cisco ASA5525-X Threat Defense (75) Version 6.2.2 (Build 362)
  UUID : 2849ba3c-ecb8-11e6-98ca-b9fc2975893c
  Rules update version : 2017-03-15-001-vrt
  VDB version : 279
  ----------------------------------------------------

  Products Confirmed Not Vulnerable

  Cisco has confirmed that the AnyConnect Secure Mobility Client is not vulnerable.
  
  No other Cisco products are currently known to be affected by this vulnerability.
  

Workarounds

• There are no workarounds that address all the features that are affected by this vulnerability. The management access to the security appliance can be restricted to known, trusted hosts using the CLI command http . Please refer to the Enable HTTP Service section in the Cisco Guide to Harden Cisco ASA Firewall for further information.

Fixed Software

• Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license: http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html

  Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.

  In all cases, customers should ensure that the devices to upgrade contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

  Customers Without Service Contracts

  Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC: http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html

  Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.

  Fixed Releases
  
  In the following tables, the left column lists major releases of Cisco ASA Software. The right column indicates whether a major release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. Customers should upgrade to an appropriate release as indicated in this section.

  Cisco ASA Major Release	First Fixed Release
  8.x1	Affected; migrate to 9.1.7.23
  9.01	Affected; migrate to 9.1.7.23
  9.1	9.1.7.23
  9.2	9.2.4.27
  9.31	Affected; migrate to 9.4.4.16
  9.4	9.4.4.16
  9.51	Affected; migrate to 9.6.4.3
  9.6	9.6.4.3
  9.7	9.7.1.21
  9.8	9.8.2.20
  9.9.1	9.9.1.2
  9.9.2	9.9.2.1

  ¹ASA Software releases prior to 9.1, including all 8.x releases, and ASA releases 9.3 and 9.5 have reached End of Software Maintenance. Customers should migrate to a supported release.

  The software is available for download from Cisco Software Center by navigating to Products > Security > Firewalls > Adaptive Security Appliances (ASA) > ASA 5500-X Series Firewalls where there is a list of ASA hardware platforms. The majority of these software releases are listed under Interim.
  
  FTD Software
  
  In the following table, the left column lists major releases of Cisco FTD Software. The right column indicates whether a major release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. Customers should upgrade to an appropriate release as indicated in this section. The FTD software images will be posted as they become available.
  
  

  Cisco FTD Major Release	First Fixed Release
  6.0.0	Affected; migrate to 6.0.1 HotFix or later
  6.0.1	Cisco_FTD_Hotfix_BH-6.0.1.5-1.sh (All FTD hardware platforms except 41xx and 9300) Cisco_FTD_SSP_Hotfix_BH-6.0.1.5-1.sh (41xx and 9300 FTD hardware platform)
  6.1.0	Cisco_FTD_Hotfix_DZ-6.1.0.7-1.sh (All FTD hardware platforms except 41xx and 9300) Cisco_FTD_SSP_Hotfix_DZ-6.1.0.7-1.sh (41xx and 9300 FTD hardware platform)
  6.2.0	Cisco_FTD_Hotfix_BN-6.2.0.5-3.sh (All FTD hardware platforms except 41xx and 9300) Cisco_FTD_SSP_Hotfix_BN-6.2.0.5-3.sh (41xx and 9300 FTD hardware platform)
  6.2.1	Affected; migrate to 6.2.2 HotFix
  6.2.2	Cisco_FTD_SSP_FP2K_Hotfix_AN-6.2.2.2-4.sh.REL.tar (21xx FTD hardware platform) Cisco_FTD_SSP_Hotfix_AO-6.2.2.2-1.sh.REL.tar (41xx and 9300 FTD hardware platforms) Cisco_FTD_Hotfix_AO-6.2.2.2-1.sh.REL.tar (All other FTD hardware platforms)
  6.2.2 (Azure)	6.2.2-2011

  ¹ If 6.2.2-201 is upgraded with the 6.2.2.1-73 patch, then Cisco_FTD_Hotfix_AO-6.2.2.2-1.sh.REL.tar must be applied to address the vulnerability described in this document. If any other patch version is applied to 6.2.2-201, this vulnerability will remain addressed in FTDv.

  The software is available for download from Cisco Software Center by navigating to Products > Security > Firewalls> Next-Generation Firewalls (NGFW) where there is a list of possible FTD hardware platforms.

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is aware of public knowledge of the vulnerability that is described in this advisory. Cisco PSIRT is aware of attempted malicious use of the vulnerability described in this advisory.

Source

• Cisco would like to thank Cedric Halbronn from the NCC Group for finding and reporting this vulnerability.

URL

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180129-asa1

Revision History

• Version	Description	Section	Status	Date
  2.4	Updated the Fixed Release table for ASA to give both options for the 9.9.1 and 9.9.2 code train fix.	Fixed Software	Final	2018-May-17
  2.3	Updated fixed release information for FTDv on the Microsoft Azure Marketplace. Added a horizontal line to Summary to separate the February 5 update text from the original summary text.	Fixed Software	Final	2018-February-16
  2.2	Corrected required config for MUS feature; further clarified the vulnerable FTD configuration in order for the vulnerability to be exploited; updated on attempted malicious use.	Vulnerable Products, Exploitation and Public Announcements	Final	2018-February-07
  2.1	Updates to which FTD release relates to which FTD hardware platform.	Fixed Software	Final	2018-February-05
  2.0	Updates to the type of attack vectors that can exploit this vulnerability and changes to the fixed software releases.	Summary, Vulnerable Products, Products Confirmed Not Vulnerable, Workarounds, and Fixed Software	Final	2018-February-05
  1.3	Further clarified the vulnerable ASA configuration in order for the vulnerability to be exploited.	Vulnerable Products	Final	2018-January-30
  1.2	Updated the First Fixed Release table with information on the 8.x code train and corrected the First Fixed Release information for 9.9.	Fixed Software	Final	2018-January-29
  1.1	Clarified that Cisco PSIRT is not aware of any malicious use of the vulnerability described in this advisory.	Exploitation and Public Announcements	Final	2018-January-29
  1.0	Initial public release.	-	Final	2018-January-29

  Show Complete History...